In recent years, power is being generated from a variety of energy sources such as thermal, hydro, wind, and solar energy sources. However, power shortages do occur for reasons such as resource insufficiency and difficulty in ensuring a stable supply. Thus, apartments, factories, etc., may be provided with batteries to be prepared for emergencies such as power shortage or stoppage.
Patent Literature 1 discloses a power supply system able to supply more power to a load when a power stoppage occurs. Further, Patent Literature 2 discloses a technique of supplying power by connecting a power generator such as a solar cell to an electrical outlet. Further, Patent Literature 3 discloses a reverse-tidal-current-preventing systematically interconnecting system that, in a power supply system, prevents adverse effects to a load from reverse power flow and ensures rapidity of resumed operation of a power system after power stoppage.